1. Field of the Invention
This invention relates to an image processing method and an image processing system which project computer-controlled images on image display means and to an experience simulation system which uses the method and the system.
2. Description of the Prior Art
Simulation systems such as computer-controlled video game systems and experience-simulation systems have been used. In particular, experience-simulation systems for a moving object such as a car or an airplane to move in a three dimensional space and competing in scores and for times or experiencing unusual experiences such as motorcycles games, driving games, flight simulation games and are popular. This type of experience simulation system has a program processing unit which processes programs and data, an image display means such as a CRT or liquid crystal display screen on which computer-generated video is projected, and an operation section which allows the player to control the program processing units. There are many types of operation unit. That is, not only a control panel on which buttons and levers are provided but also the model of a vehicle, such as the body of a motorcycle or the cockpit of a racing car or an airplane, is used depending upon the type or operation of the unit used in the game.
Video images are displayed on the image display means of the experience simulation system. For example, in a driving game, a plurality of previously-stored, three-dimensional objects are arranged in a virtual three-dimensional space called a game field. FIG. 5 is an example of a game field where three-dimensional objects are arranged. Along the driving course are arranged three-dimensional objects such as the building 500, trees 501, guardrail 502, and vehicle 503.
The experience simulation system displays the three-dimensional objects on the image display means as follows: that is, it looks through the virtual three-dimensional space containing the three-dimensional objects from a given viewpoint, projects image information about each object represented as the perspective coordinates onto the projection screen some distance away from the viewpoint, and draws the two-dimensional projection images on the projection screen in the image display means. For example, as shown in FIG. 6, the system looks through the object 301 arranged in the three-dimensional space from the viewpoint 0 and projects it onto the projection screen 300 that is xe2x80x9chxe2x80x9d away from the viewpoint 0 in the form of two-dimensional projection image 302. In this case, the system divides the three-dimensional object 301 into a plurality of polygons and, based on the coordinates (X, Y, Z) of the vertexes of each polygon, calculates the coordinates (XS, YS) of each vertex of the image to be displayed on the projection screen, using the formula (1).
XS=(X/Z)xc3x97hxe2x80x83xe2x80x83[Formula 1]
YS=(Y/Z)xc3x97hxe2x80x83xe2x80x83(1)
The player controls the operation section of the experience simulation system to drive a motorcycle or a racing car or to pilot an airplane to participate in a race or a combat, and competes for times and scores. In this case, as the moving object moves around in the virtual three-dimensional space, the position of the viewpoint 0, which is relatively associated with the moving object, also moves. That is, as the distance between the viewpoint 0 and each object 301 changes, the shape of the two-dimensional projection image 302 displayed on the image display means 300 also changes, giving the player an illusion that the object moves in the three-dimensional space.
However, in the traditional experience simulation system, the distance H1 from the viewpoint 0 to the projection screen Z1 with the view field angle of a is fixed, as shown in FIG. 7. Because of this, the speed of a moving object is directly reflected on the screen; it can be neither increased nor decreased. A speed higher or lower than that of the moving object, if projected on the screen, would make the player feel more realistic. However, such a technology has not been introduced.
In addition, in a system where this type of perspective conversion technology is used, moving a moving object as well as the viewpoint at a high speed reduces the effective visual area on the projection screen, makes three-dimensional objects difficult to recognize in the three-dimensional space, and decreases the reality of the image produced by the experience simulation system.
It is difficult for human eyes to recognize moving objects which move at higher a speed than, prescribed speed. This also applies when a three-dimensional object is projected on the projection screen. And, the more speedily a three-dimensional object moves within the unit time (T), the more difficult it becomes to recognize the object. In FIG. 7, assume that the two object, the object P and the object R which is more distant from the viewpoint along the z axis but which has the same coordinates X and Y as those of P, have moved toward the viewpoint 0 for the distance of M and that they have reached P and Q respectively. The new positions of the points on the projection screen Z1 are P1, Q1, and R1, and the movement distances of objects P and R are DP1 and DR1. As shown in this figure, although the two objects have moved toward the viewpoint for the same distance along the z axis, the movement distance of the object closer to the viewpoint is larger than that of the object more distant from the viewpoint. And, the object closer to the projection screen is projected in a location closer to the circumference of the projection screen.
This indicates that, even when the amount of movement (M) toward the viewpoint within a specified time (T) (speed of movement toward the viewpoint) is the same, the movement distance on the projection screen (DP1) within the same time (T) of an object located closer to the viewpoint and projected closer to the circumference of the projection screen becomes larger. This makes it more difficult for humans to recognize a moving object located closer to the circumference of the screen. Conversely, the movement distance on the projection screen (DR1) of an object located more distant from the viewpoint and projected smaller on the projection screen is smaller in relation to the amount of movement (M). This makes it less difficult for humans to recognize a moving object even when the object moves faster in relation to the viewpoint and the object moves faster to go the distance M. As a result, the higher movement of an object reduces the effective visual area on the projection screen.
This fact is evidenced by the symptom, called a stricture of a view field (an effective-visual area reduction), we usually experience while driving a car. When we are driving a car at a high speed, the effective visual area is reduced. As a result, we find it difficult to recognize the objects closer to our viewpoint but find it less difficult to recognize distant objects. But, the fact is that, when we are driving a car, we look not only the at objects right in the front but those surrounding them. This makes up the for reduction in the effective visual area, allowing us to view a broad landscape.
In an experience simulation system, the viewpoint is always on a moving object and the projected direction always keeps track of an object that is moving. Thus, the image processing method used in the traditional experience simulation system reduces the visual area as the speed of a moving object increases, because it does not allow the player to look at something surrounding the moving object. It permits the player to recognize only objects in the center of the image display means and therefore degrades the reality of the game when the moving object is moving at high speed.
This invention seeks to solve the problems associated with the prior art described above. It is an object of this invention to provide an experience simulation system which makes a player feel an object moving faster or slower than it actually does at virtual speed. It is another object of this invention to provide an experience simulation system which does not reduce the effective visual area on the projection screen even when a moving object moves fast as well as an image processing method and an image processing system for use with the above-mentioned experience simulation system and other types of image display system.
To achieve the above object, an image processing method according to this invention is an image processing method which comprises: providing a virtual three-dimensional space containing three-dimensional objects, providing a virtual viewpoint relatively associated with a virtual moving object moving in the virtual three-dimensional space, providing a virtual projection screen on which the objects in the virtual space viewed from the viewpoint are projected, and displaying the two-dimensional projection image of the three-dimensional objects, projected on the projection screen, onto image display means, in which the relative distance between the viewpoint and the projection screen varies according to the movement speed of the virtual moving object.
And, the image processing method comprises: providing a virtual three-dimensional space containing three-dimensional objects, providing a virtual viewpoint relatively associated ith a virtual moving object moving in the virtual three-dimensional space, providing a virtual projection screen on which the objects in the virtual space viewed from the viewpoint are projected, and displaying the two-dimensional projection image of the three-dimensional objects, projected on the projection screen, onto image display means, in which the view field angle of the viewpoint to the projection screen, viewed from the viewpoint, varies according to the movement speed of the virtual moving object and in which the two-dimensional projection image on the projection screen is displayed in a fixed-sized display area on the image display means.
The method according to this invention with the above configuration has the following effects:
(1) The view field angle of the viewpoint to the projection screen may be changed according to the speed of a moving object. For example, when the moving object moves faster, the visual angle to the projection screen becomes large, allowing a larger range of the three-dimensional space to be projected in the same area on the projection screen. As a result, even if the view field is strictured as the moving object moves faster, the view field angle becomes larger and, therefore, a larger range of the three-dimensional space is projected in the same area on the projection screen. This eliminates an extreme reduction in the object that is displayed even if the moving object moves faster.
(2) A larger view field angle results in a smaller projection image on the projection screen or on the display means. This reduces the movement distance of a moving object on the projection screen or on the display means when the moving object approaches another object. As a result, a moving object that moves too fast to be recognized on a projection screen which has a smaller view field angle and on which the movement distance is large could be recognized.
(3) A larger view field angle to the projection screen makes an object look smaller on the projection screen or on the image display means, making the player feel that the object is in the distance. Actually, however, because the distance between the object and the viewpoint is the same and the movement speed of the moving object is constant, the time required for the moving object to reach the object remains unchanged. This makes the player feel as if the distant object was approaching the object in less time speedily.